Fuel cells are electrochemical energy conversion devices that convert an external source fuel into electrical current. Many common fuel cells use hydrogen as the fuel and oxygen (typically from air) as an oxidant. The by-product for such a fuel cell is water, making the fuel cell a very low environmental impact device for generating power.
The challenge of hydrogen storage and generation has limited the wide-scale adoption of fuel cells. Although molecular hydrogen has a very high energy density on a mass basis, as a gas at ambient conditions it has very low energy density by volume. The techniques employed to provide hydrogen to portable applications are widespread, including high pressure and cryogenics, but they have most often focused on chemical compounds that reliably release hydrogen gas on-demand. In some chemical reaction methods for producing hydrogen for a fuel cell, hydrogen storage and hydrogen release are catalyzed by a modest change in temperature or pressure of the chemical fuel. In other reaction methods, liquid reactants may be contacted with solid reactants to generate product gases.
One typical problem with chemical hydrolysis is the tendency of the liquid byproducts to foam, which creates control and volume efficiency problems. High flow velocities may contribute to the foaming of slurry phase products. In some instances, foaming byproducts can block the flow area and relief devices, which may lead to over pressure issues. Another common issue with hydrolysis based reactions is that crystal hydrate byproducts are often formed. This traps some unreacted water into a water reactive material. The stability of these hydrates is often temperature dependent, which byproduct release water at elevated temperatures. If energy is later added either during operation, transport or storage, it is possible to release that water and generate hydrogen either unexpectedly or uncontrollably. Since water reactive control systems typically control water injection to manage gas pressure, a build up a hydrated byproduct represents a loss of control.
Thus, there is a need for improved hydrogen generation systems and methods that overcome many, or all, of the above problems or disadvantages in the prior art. The disclosure is directed to these and other important needs.